The 44-year-old had been in charge at the Allianz Riviera since June 2018, his second head coach job following two seasons in MLS with New York City FC.
He was due to be out of contract at the end of the campaign but Nice have taken the decision to terminate the former Arsenal star’s deal early.
The decision was made following Thursday's 3-2 loss to Bayer Leverkusen, which was overshadowed by protests before kick-off with supporters demanding Vieira step aside.
That defeat ensures Nice can no longer advance to the Europa League knockouts and they are 11th in Ligue 1 after going more than a month without picking up a point.
Nice confirmed the news on their official website on Friday and announced Adrian Ursea will step up from his previous role as assistant boss to take temporary charge of the first team.
"In a meeting conducted after last night's match, the Nice board informed Patrick Vieira of their decision to end their collaboration," Nice said in a statement.
"The Rouge et Noir has decided to appoint Adrian Ursea as head coach of the club's professional first team, as of today."
Vieira guided Nice to seventh place in his first season at the helm and improved on that by finishing fifth in last term's curtailed campaign on a points-per-game basis.
"Patrick put all his heart and professionalism into his service for OGC Nice over the last two and a half years of their collaboration," the statement added.
"The Nice board sincerely thanks the former France international for his commitment and dedication to the development of the club and wishes him every future success in his coaching career."
First up for Ursea, who has also worked alongside Lucien Favre in the Nice dugout, is a league trip to Reims on Sunday.